Drying drum



W P. DAPSES Jan. 15, 1963 DRYING DRUM Filed NOV. 5, 1959 INVENTORWILLIAM E DAPSES ATTORNEY Uited States Patent 3,073,038 DRYING DRUMWilliam P. Dapses, North Attleboro, Mass, assiguor of one-half toWoodrow C. Lodding, Boston, Mass. Filed Nov. 5, 1959, Ser. No. 851,182 2Claims. (Cl. 34-410) This invention relates to a new and improved methodand apparatus for drying materials in general and particularly materialsin the form of webs which may be dried to some extent in a preliminarymanner but which are finally more or less completely dried by theapplication of heat thereto. The invention also contemplates drying ofchemicals or other materials which may be powdered, granulated orcomminuted.

One of the principal objects of the invention resides in the provisionof a novel apparatus and method for drying which decreases greatly theinterval of time necessary for the drying steps and which also reducesthe amount of apparatus utilized for such purposes; and one illustrationin this regard relates to the paper-making industry wherein a web ofpaper pulp is fed to a thermal section for drying and includes heatedcylinders overwhich the web passes, usually with a felt on the paperholding the same to the surface of the cylinder over which the paper ispassing at the particular moment.

The present invention also resides in the provision of a foraminous orporous member having a surface over which the web is adapted to betraveled, this member being provided at the side opposite the web with asource of dry heat obtained in any way, so that the heat is imparted tothe web through the member whereby vapor pressure is produced by theimpingement of the heat on the web and between the surface of the heatedmember and the web. The vapor is forced to move inwardly away from theweb through the foraminous or porous member, toward the source of heatwhere the humidity is kept as low as possible so that a large amount ofmoist air or vapor is accepted, thus drying the web very quickly,particularly as compared with the prior art thermal drying apparatus. Inthe prior art, the apparatus provides for heating one side of the web bymeans of an opaque or solid cylinder and driving the vapor directly butonly partially through the web and then passing the web over on anotherroll and heating the opposite side of the web. Thus the vapor in theprior art is driven away from the surface of the roll toward the centerof the web, alter nately from different sides thereof, increasing thelength of time required for thermal drying, as opposed to the muchfaster operation of the present invention which provides for themoisture, i.e., vapor, to be extracted from the web at the heated siderather than being pushed through the web from the heated to the coolerside.

Other objects and advantages of the invention will appear hereinafter.

Reference is to be had to the accompanying drawings, in which FIG. 1 andFIG. 2 are diagrammatic views illustrating the prior art;

FIG. 3 is a diagrammatic view illustrating the present invention; and

FIG. 4 is a sectional view illustrating a modification of the presentinvention.

In the prior art as shown in FIG. 1, an opaque or solid cylinder or rollis heated with steam and over the surface thereof there is passed theweb 12 which may be for instance of paper. Over the paper there isusually provided a felt belt or the like 14 which is adapted-to pressthe web into intimate contact with the heated surface of the roll.

The arrows show the direction of the vapor which of course cannot passthrough the solid surface of the steamheated roll but instead tends tobe forced outwardly in the direction of the arrows into the felt. Thesurface of the web next to the cylinder tends to dry but the moisture isforced into the remainder of the thickness of the web.

It is to be understood that this action is repeated time after timethrough a stack of cylinders but in passing from one cylinder toanother, the heat is applied to the opposite sides of the web. Thereforelooking at FIG. 1 it will be seen that the vapor is driven from thesurface of the roll through the paper toward the felt, but one pass ofthe web over the roll is not sufiicient to drive much of the moistureinto the felt, or into the atmosphere if the felt is not present, andwhen the next roll is applied to the opposite surface of the paper, theaction is to drive the vapor in the opposite direction back into theweb. Obviously this results in a lengthy period of time required toextract the moisture from the paper web.

On the other hand, in the present invention there is provided acylindrical or other shaped member which is foraminous or porous. Theopenings passing through the member may be relatively small but thereshould be provided a great number of small passages completely throughthe member from the exterior surface to the interior surface thereof.This is illustrated in FIG. 3 where the member is indicated at 16 and isshown as a roll, and it is made of any kind of material which willprovide passages therethrough as indicated at 18, see also the arrows inthis figure. The web is shown at 20.

The interior of the roll 16 is provided with a dry heat which may bederived from electricity, gas, oil, or other source. The humidity of theinterior of this roll is kept at a minimum humidity whereas of course inthe prior art the steam heat for the rolls 10 adds to the atmosphericmoisture rather than subtracting from it.

In any event it will be seen that as the web 20 passes over the surfaceof roll 16, it comes in contact with the heated surface which isprovided with a great number of small through holes. A vapor pressure isset up at the surface of roll 16, i.e., just at the line of the surfaceof the roll where the paper hits it. The vapor under pressure finds aready outlet and is forced to move inwardly in the direction of thearrows through the holes in the foraminous roll. This vapor does notcondense at the interior of the roll because of the low humidityprovided therein, but as vapor it proceeds out the ends of the rolls ormay be collected in any Way desired by being cooled at suitable points.

Instead of the porous roll 16, a relatively large cylinder of stainlesssteel or the like may be punched to provide holes 22 for the samepurpose. The operation of the drying apparatus will be the same as abovedescribed and the vapor will be forced in through holes 22 in the samemanner as described above with relation to the porous roll in FIG. 3.

No felt such as that at 14 is needed in the invention in this casebecause due to the presence of the holes, the paper web is held thereto.If a felt is utilized, how ever, the same may be provided withoutdeparting from the scope of the invention, and of course such felt willnot take up or tend to bar the vapor escape.

It will be seen that this invention provides a greatly improved methodand apparatus for drying materials particularly in the form of webs.These webs may be paper, textiles, plastics, etc. On the other hand, theapparatus and method may also be used for drying granulated materialparticularly where the granules are larger than the holes in the surfaceof the roll so that the granules continue to pass over the roll surfacewithout being drawn inwardly with the vapor pressure. The moisture iscontinually drawn from the interior of the web 3 outwardly to the heatedsurface thereof regardless of the transposition of the web inthe newmethod as described in the old method in FIG. .2. In the old method, themoisture is attempted to be pushed inwardly from one surface through theweb toward the other surface, so that instead of in effect drying a halfof the thickness of the web at the heated side, as in the new method, inthe old method the moisture has to be pushed through what amounts to theentire depth of the paper. Instead of being continually drawn outwardly,as for instance from the center to the surfaces of the Web, it is pushedinwardly from the surfaces toward the center in the prior art. Thereforeit will be clear that the method of operation in the present inventionis a great improvement over the prior art particularly with respect tothe time elemer involved and also to the fact that the number of rollsor cylinders used in drying the web can be reduced to about one-fifththe number ordinarily used in the prior art.

The material of the member 16 may be cintered metal, porous ceramic,plastic or metal, felted or matted and fused, etc. The member 16 shouldbe relatively heavy to hold and conduct the heat through the materialthereof, and it is observed that condensation in the holes 18 or 22 isprevented by the conducted heat.

Higher heats may be utilized in this invention because no cookies orripples will be produced as in the prior art when the heat rises over acertain reading and when processing coated or impregnated papers, theinvention avoids migrating. This is due to the fact that the vehicleused in coating or impregnating is released easier and faster in the newmethod.

Having thus described my invention and the advantages thereof, I do notwish to be limited to the details herein disclosed, otherwise than asset forth in the claims, but what I claim is:

l. Drying apparatus of the class described comprising a heated surfaceover which moist material to be dried passes in intimate contacttherewith, said surface being forarninous, a source of substantially dryheat at one side of said surface, said material being at the oppositeside thereof, said heat passing through said foraminous surface andbeing applied to one side of the mass of the material and forming asource of continuous vapor pressure between the foraminous surface andthe mass of material, the vapor escaping through the for-aminous surfacetoward the source of heat, and means providing for dispersal of thevapor, said voraminous surface being in the form of a spongy hard porousmaterial.

2. Drying apparatus of the class described comprising a heated roll overwhich moist material to be dried passes in intimate contact therewith,said roll having a foraminous porous surface, a source of dry heatWithin said roll, said heat providing a continuous source of vaporbetween the surface of the roll and the adjacent surface of thematerial, said vapor pressure escaping from the point where it is formedinwardly of the roll through the roll surface toward the source of heat,at least one end of the roll being open to provide for dispersal of thevapor, said roll being in the form of a hard spongy mass includingcontinuous passages from one surface thereof to the other surface.

References Cited in the file of this patent UNITED STATES PATENTS697,3i2 Atwood Apr. 8, 1902 2,664,391 Schmidt Sept. 15, 1936 2,074,455Carleton Mar. 23, 1937 2,299,662 Thaler Oct. 24, 1942 2,436,028Wiegerink Feb. 17, 1948 FOREIGN PATENTS 1,158,265 France Jan. 20, 1958

1. DRYING APPARATUS OF THE CLASS DESCRIBED COMPRISING A HEATED SURFACEOVER WHICH MOIST MATERIAL TO BE DRIED PASSES IN INTIMATE CONTACTTHEREWITH, SAID SURFACE BEING FORAMINOUS, A SOURCE OF SUBSTANTIALLY DRYHEAT AT ONE SIDE OF SAID SURFACE, SAID MATERIAL BEING AT THE OPPOSITESIDE THEREOF, SAID HEAT PASSING THROUGH SAID FORAMINOUS SURFACE ANDBEING APPLIED TO ONE SIDE OF THE MASS OF THE MATERIAL AND FORMING ASOURCE OF CONTINUOUS VAPOR PRESSURE BETWEEN THE FORAMINOUS SURFACE ANDTHE MASS OF MATERIAL, THE VAPOR ESCAPING THROUGH THE FORAMINOUS SURFACETOWARDS THE SOURCE OF HEAT, AND MEANS PROVIDING FOR DISPERSAL OF THEVAPOR, SAID VORAMINOUS SURFACE BEING IN THE FORM OF A SPONGY HARD POROUSMATERIAL.